Presentation
Presentation after resection of a squamous cell carcinoma (SCC) with progressive facial nerve paresis and complaints of facial pain on the right. Note: no preoperative imaging. Only a CT and MRI are presented for evaluation of the facial structures.
Patient Data
See case discussion and highlighted images below.
See case discussion below.
See case discussion below.
Case Discussion
This case shows perineural tumour spread in different directions.
First, there is tumour spread involving the infraorbital nerve on the right side. This is visible as an obliterated preantral fat pad with also thickening of the infraorbital nerve. The infraorbital nerve is the most anterior branch of the maxillary nerve (V2). Coursing through the infraorbital canal, the infraorbital nerve exits the orbit via the inferior orbital fissure where it courses more posterior through the pterygopalatine fossa.
The pterygopalatine fossa is located close to the apex to the orbit (posterior to the maxilla; between the maxillary tuberosity and the pterygoid process). This fossa should show complete fat density (CT) or intensity (MRI) on imaging studies. Posterior to the pterygopalatine fossa V2 would extend through the foramen rotundum extending into the lateral aspect of the cavernous sinus.
There is also tumour spread visible along the supraorbital nerve which is a division of V1. Through the superior orbital fissure V1 passed dorsally into the cavernous sinus.
Another pathway shown in this case is through the so-called superficial muscular aponeurotic system (SMAS). The SMAS is a fibrous network that connects the facial muscles with the dermis.
The SMAS merges with the temporoparietal and parotid fascia.
The parotid fascia is pierced by the auriculotemporal nerve which is a division of the mandibular nerve (V3). This auriculotemporal nerve has a few small branches which communicate with the facial nerve. This enables tumour spread involving both the facial nerve (VII) and the auriculotemporal nerve (V3).
Normally the auriculotemporal nerve isn't visible on cross-sectional imaging. A pathologic (thickened) nerve however may be visible. The auriculotemporal nerve is located retromandibular and on both sides of the mandibular ramus at the level of the maxillary artery. Detailed anatomy is clearly depicted in the referenced article by Ilona Schmalfuss 1.
Conclusion
This case shows a combination of perineural tumour spread involving the trigeminal nerve and the facial nerve.
Regarding the trigeminal nerve there is involvement of:
- supraorbital nerve (division of V1)
- infraorbital nerve (division of V2) touching the lateral border of the pterygopalatine fossa
- auriculotemporal nerve (division of V3) spreading up to the foramen ovale
- facial nerve (VII) via the SMAS and connections between the auriculotemporal nerve/facial nerve
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